A review of the patent art and literature will reveal that substantial work has been conducted to produce films, filaments, and shaped articles including impregnated fabrics such as paper from amylose and amylose derivatives.
Amylose is a linear polymer found widespread in many types of plants. It can be obtained by the fractionation of starch which varies in content from a few percent in some types to over 60% in specialty high amylose starches. Amylose is a polymer and consists of chains of .alpha.-D-glucopryanose units linked (1.fwdarw.4) and has a molecular weight of from about 50,000-200,000. Its structure is similar to that of cellulose except that it is alpha linked whereas cellulose is beta linked. Apparently, because of this difference in chemical linkage, cellulose is a relaxed linear chain which crystallizes into fibrous materials whereas amylose is a coiled of spiral chain which is capable of helical conformation and does not crystallize into a fibrous material.
The many similarities between cellulose and amylose permit similar processes to be carried out and products to be made. For example, similarly to cellulose, amylose can be made into filaments by making esters of amylose, e.g., amylose acetate, amylose acetate-butyrate and spinning these esters into fibers. Amylose can also be made into films in like manner as cellulose which have been used as a packaging material for detergents, as protective coatings for food packaging and in general where self-supporting films are desired. For example, one type of film can be made by forming amylose xanthate employing a process similar to the viscose process for making cellulose films and casings and then regenerating the amylose.
Even though there has been considerable interest in producing films, filaments, and shaped articles from amylose and amylose derivatives, the films have not been widely used. Although the material is attractive economically and further because it is edible whereas cellulose is not, the films, filaments, etc., have not had the desired physical properties to make the products widely accepted on a commercial basis. One of the reasons for non-acceptance is that generally films and filaments have been extremely brittle. Particularly in the artificial sausage casing field, the films have not had sufficient elasticity to withstand the rigid stuffing conditions required for sausage manufacture and, therefore, suffered a high degree of breakage in the stuffing operation. Secondly, the casing, presumably because of the lack of desirable elasticity, did not shrink with the sausage during cooking. The homemaker found these casings, which extended from the sausage, to be unsightly and undesirable.